Spark plug



Nov. 3, 1942. c. R. BUENING SPARK PLUG Filed Dec. 20, 1940 R O T N E V m ijharlas HEmEmz-L ATTORNEY Patented Nov. 3, 1942 SPARK PLUG Charles B. Buening, Milwaukee, Wis., asslgnor to Globe-Union Inc., Milwaukee, W

tion of Delaware M ca o n- Application December 20, 1940, Serial No. 370,959

21 Claims. (Cl. 123-189) the high tension terminal at the outer end of the center electrode to the metal shell or gland nut, and to accomplish this in a simple and comparatively inexpensive and practical while preserving all of ,the-advahtagcs of the standard or conventional spark plug.

Other .objects and advantages reside in cert ain rfovel features of the construction, arrangement, and combination of parts, which will be hereinafter more fully described and particulars ly.pointed out in the appended claims, reference being had to the accompanying drawing forming a part of this specification, and in which:

'Figure l is a view partly in vertical diametrical cross section and partly in side elevation showing a spark plug of the gland nut type embodying one iorm of the present invention;

Figure 2 is a view similar to Figure 1 and showing the same form of the invention incorporated in a spark plug'of the so-called one-piece crimped shell type;

Figure 3 1s a view similar to Figures 1 and 2 but showing another form of the present invention embodied in a spark plug of the gland nut type;

Figure 4 is a view similar to Figures 1 to 3 but showing the form of the invention illustrated in Figure 3 incorporated in o. spark plug of the so-called one-piece crimped shell type: and

Figure 5 is a. fragmentary view similar to Figure 4 but showing a structural variant of the form 40 of the invention illustrated in Figure 4.

Referring to the drawing, it will be seen that in all embodiments of the present invention a spark plug is provided which comprises a bushing or metallic shell-like body M which has its lower end reduced and externally threaded, as at H, to adapt it to be screwed into an internally threaded opening of a cylinder head of-an internal combustion engine. The outer end of the metallic shell I0 is provided with a hexagon formation II to adapt it to coact with a wrench or suitable tool to facilitate the installation and re moval of the plug. An insulator [3, usually of porcelain or ceramic material, is associated with posed between the insulator ll d the metallic shell II in the usual way. Anouter gasket I5 is also provided.

In the construction shown in Figures 1 and 3 5 a packing gland nut I is threaded into the upper end of the metallic shell l0 and engages the gasket 15, thereby hermetically sealing the packing nut It to the insulator ll of the plug and also compressing the gasket II to effect a hermetic seal between the insulator l3 and the shell In lieu of utilizing a packing or gland nut, such asnut H, for compressing the inner and outer gaskets l4" and i5, and thereby setting up the desired seal between the insulator i3 and the shell In, this may be accomplished by spinning, crimping, or forming over the'upper portion III of the metallic shell in the manner illustrated in Figures 2, 4, and 5.

A center electrode I1 is combined withthe insulator II in the usual way. The inner end-pf the center electrode is cooperatively related tote one or more side electrodes II. The outer end or high tension terminal of the center electrode is equipped with the usual terminal nut It.

In the form of the invention shown in Figure 1, a cap of electrical insulating material, designated generally at 20, is applied over the portion of the insulator which is adjacent the gland nutv it. The cap ifl has a thick body portion 2| pro-- vided with a central opening 22 through which a, portion of the insulator Ii extends. The flange 2; of the cap projects down over the outside of the gland nut l6 and bears against the top of the metallic shell II. The cap is molded or otherwise formed of insulating material, such as rubber, synthetic rubber, synthetic elastic insulating ma terial, elastic insulating material, 0!. the like.

Preferably the internal diameter of the opening 22 in the body 2| thereof is slightly less than the external diameter 01' the portion of the insulator l3 which it engages so that the body 2| of the cap must be stretched to assemble it with the insulator II, and when assembled is still slightly stretched so as to insure a tight surface-to-surface contact or fit between the inner wall of the opening 22 and the portion of the outer periphcry of the insulator I3 with which the inner wall of the opening 22 engages. This desired contact and tight fit ma further be enhanced by cementing the inner wall of the opening 22 to the portion of the insulator I3 which it engsges.

In some instances, also, it may be desirable to further insure the maintenance of the assemthe metallic shell Ill. ,Aninner gasket I4 is intery 01 the insulating c l 0 with the insulator ll, and this may be accomplished by forming an integralannularjrib or head 24 on the insulator I! in 'such'position that it engages the top surface of the cap 2| to positively retain it in place.

When assembled in the manner described, the protective or shielding cap provides a high and effective resistance to electrical flash-over or discharge from the high tension terminal is at the outer end of the center electrode to the packlng or gland nut it and'to the metallic shell It.

In the form of the invention shown in Figure 2, a similar protective capor shield, designated generally at II, is provided, and in fact in all essential respects is the same as the protective or shielding cap 2| except that its dimensions are varied to adapt it to contact with the so-called one-piece crlmped shell type of spark plug. In this instance a shoulder 2' may be formed on the insulator II to engage the top of the cap 25 for positively holding or retaining it in position. The under side of the bodyof the cap 25, as well as its flange 28, are preferably in close and tight engagement with the crimped-o'ver end ill of the shell ll, due to the fact that the cap is stretched wheniltted over these parts. However, when the caps 21:. d 25 are cemented to their respective insulato I! it is not necessary to provide the rib It in the one instance, nor the shoulder 1! in the other.

In the i'ormof the invention shown in Figure 3, in lieu of a molded or preformed cap of electric insulating elastic material of the relatively substantial dimensions shown and described, the cap may be in the form of a coating or layer of electrical insulating material, designated genorally at 80, applied around the top and over the outside of the gland nut and across the top of the metallic shell II in the manner illustrated in the drawing. This cap I! of electrical insulating material may be painted, sprayed, molded, pressed, fused, or cemented to the surfaces to which it is applied. Any suitable plastic material, which is electrically insulating, has the requisite bonding properties, is capable of withstanding the" temperature to which it is sublooted, and chemically inert in its environment, maybe used, or any liquid electrical insulating material, which is settable after application, and which has the propertia mentioned, my be employed. A cement which has synthetic rubber as its base, has been successfully used. Insulating coatings of ceramic or porcelain insulating cement or enamel, or high dielectric insulating enamel, paint, or plastic, will serve efleotlvely.

In the form of the invention shown in'Figure 4, a cap of electrical insulating material, designated at II. but similar to cap ii, is applied over the crimped portion of the metallic shell It, and over the upper portion of the metallic shell proper, in the manner illustrated in the drawing. This cap ll is similar in its composition to the cap 3!), the only difference between the construction shown in Figures 3 and 4 being that Figure 4 illustrates how a coating or cap of electrical insulating material may be applied to the one-piece crimped shell type of spark plug. If desired, the cap or coating of insulating material applied to the one-piece crimped type of spark plug, instead of terminating at the top of the hexagon of the metallic shell, may be extended down to cover the outer surface of the hexagon, as indicated at I! in Figure 5. Ordinarily, and preferably, however, the external dimensions of the caps 20, 25, .II and II are such as to lie within the conformation I! at the upper end of the metallic shell IQ of each plug, as it is desirable to leave the peripheral surface of the hexagon formation l2 uncovered so that its adaptability for coaction with a wrench or other suitable tool is not impaired.

In all forms of the invention there is presented a high and effective resistance to electrical flashover or discharge from the high tension terminal at the outer end of the center electrode to the metallic shell or gland nut of the spark plug, and this is accomplished without increasing the overall dimensions of the plug, or otherwise impairing its advantages and usefulness or the facility with which it may be installed or removed. In fact, the plug presents a standard or normal appearance and may be manufactured with economy and by means of facilities and from materials ordinarily available.

While I have shown and described several constructions in which the invention may be advantageously embodied, it is to be understood that the constructions shown have been selected merely for the purpose of illustration or example,

lines of the external dimensions of the hexagon 7 and that various changes in the size, shape, and

arrangement of the parts may be made without departing from the spirit of the invention or the scope of the subjoined claims.

I claim:

.l. A spark plug comprising a metallic shell, an insulator having an inner portion disposed in the shell, and an outer portion projecting outwardly therefrom, cooperating structure on the shell and on the portion of the insulator disposed therein and including metallic means at the outer end of the shell for securing and hermetically sealing the insulator to the shell, a high tension terminal projecting beyond the outer end of the insulator, and a cap of electrical insulating material covering and conforming to the contour of said metallic means and in tight surface-tosurface engagement with the part of the peripheral surface of the outer projecting portion of the insulator adjacent said means, the outer portion of the insulator projecting beyond said cap, the cap coacting with the portion of the insulator extending between the cap and the high tension terminal to provide a high and effective resistance to electrical flash-over or discharge from the high tension terminal to said means and said shell.

2. A spark plug comprising a metallic shell, an insulator having an inner portion disposed in the shell, and an outer portion projecting outwardly therefrom, co-operatlng structure on the shell and on the portion of the insulator disposed therein and including metallic means at the 'jecting beyond said cap, the'cap coacting with the portion of the insulator extending between the cap and the high tension terminal to provide a high and effective resistance to electrical flash-over or discharge from the high tension terminal to said metallic means and said shell.

3. A spark plug comprisin a metallic shell, an insulator having an inner portion disposed in the shell, and an outer portion projecting outwardly therefrom, co-operating structure on the shell and on the portion of the insulator disposed therein and including metallic means at the outer end of the shell for securing and hermetically sealing the insulator to the shell, a high tension terminal projecting beyond the outer end of the insulator, and a cap of elastic electrical insulating material surrounding and'in stretched engagement with and cemented to the outer portion of the insulator immediately above said metallic means and conforming to the contour of and covering said metallic means and overlying the outer end of said shell, the outer portion of the insulator'projecting beyond said cap, the cap coacting with the portion of the insulator extending between the cap and-the high tension terminal and providing a high and effective resistance to electrical flash-over vor discharge from the high tension terminal to said metallic means and said shell.

4. A spark plug comprising a metallic shell, an insulator having an inner portion disposed in the shell, and an outer portion projecting outwardly therefrom, co-operating structure on the shell and on the portion of the insulator disposed therein and including metallic means at the outer end of the shell for securing and hermetically sealing the insulator to the shell, a high tension terminal projecting beyond the outer end of the insulator, and a cap of elastic electrical insulating material surrounding and in stretched engagement with the outer portion of the insulator immediately above said metallic means and conforming to the contour of and covering said metallic means and overlying the outer end of said shell, the outer portion of the insulator projecting beyond said cap, the cap coacting with the portion of the insulator extending between the cap and the high tension terminal and providing a high and effective resistance to electrical flash-over or discharge from the high tension terminal to said metallic means and said shell,

the outer portion of the insulator having a downwardly facing shoulder engageable with the top of the insulating cap to positively retain it in position.

5. A spark plug comprising a metallic shell, an

insulator having an inner portion disposed in the shell and an outer portion projecting outwardly therefrom, means including a gland nut threadedly connected with the outer end of the shell for securing and hermetically sealing the insulator to the shell, a high tension terminal projecting beyond the outer end of the insulator, and a cap of electrical insulating material covering and conforming to the contour of said gland nut and in tight surface-to-surface engagement with the part of the peripheral surface of the outer projecting portion of the insulator adjacent said gland nut, the outer portion of the insulator projecting beyond said cap and coacting therewith to provide a high and efiective resistance to electrical flash-over or discharge from the high tension terminal at the outer end of the insulator to said gland'nilt and said shell.

6. A spark plug comprising a metallic shell, an insulator having an inner portion disposed in the shell and an outer portion projecting outwardly therefrom, means including a gland nut threadedly connected with the outer end of the shell for securing and hermetically sealing the insulator to the shell, a high tension terminal projecting beyond the outer end of the insulator, and a cap of elastic electrical insulating material surrounding and in'stretched engagement with the outer portion of the insulator immediately above said gland nut and conforming to the contour of and fitted over and covering said gland nut and overlying the outer end of said shell, the outer portion of the insulator projecting beyond said cap and coacting therewith to provide a high and effective resistance to electrical flashover or discharge from the high tension terminal at the outer end of the insulator to said gland nut and said shell.

7. A spark plug comprisin a metallic shell, an insulator having an inner-portion disposed in the shell and an outer portion projecting outwardly therefrom, means including a gland nut threadedly connected with the outer end of the shell for securing and hermetically sealing the insulator to the shell, a high tension terminal projectlng beyond the outer end of the insulator, and a cap of elastic electrical insulating material surrounding and in stretched engagement with and cemented to the outer portion of the insulator immediately above said gland nut and conforming to the contour of and fitted over and covering said gland nut and overlying the outer end of said shell, the outer portion of the insulator projecting beyond said cap and coacting therewith to provide a high and eifective resistance to electrical flash-over or discharge from the high tension terminal at the outer end of the insulator to said gland nut and said shell.

8. A spark plug comprising a metallic shell. an insulator having an inner portion disposed in the shell and an outer portion projecting out-' wardly therefrom, means including a gland nut threadedly connected with the outer end of the shell for securing and hermetically sealing the insulator to the shell, a high tension terminal projecting beyond the outer end of the insulator, and a cap of elastic electrical insulating material surrounding and in stretched engagement with the outer portion of the insulator immediately above said gland nut and conforming to the contour of and fitted over and covering said gland nut and overlying the outer end of said shell. the outer portion of the insulator projecting beyond said cap and coacting therewith to provide a high and effective resistance to electrical flashover or discharge from the high tension terminal at the outer end of the insulator to said gland nut and said shell. the outer portion of the insulator having a downwardly facing shoulder immediately above and in engagement with the top of the insulating cap to positively retain it in position.

9. A spark plug comprising a metallic shell, an insulator having an inner portion disposed in the shell and an outer portion projecting outwardly therefrom, means including an inward crimp on the outer end of the shell for securing and heri metically sealing the insulator to the shell, a high tension terminal projecting beyond the outer end of the insulator, and a cap of electrical insulating material covering and conforming to the contour of said inward crimp and in tight surface-tosurface engagement withthe part of the peripheral surface of the outer projecting portion of the insulator adjacent said inward crimp, the outer portion of the insulator projecting beyond the cap and coacting therewith to provide a high and effective resistance to electrical flash-over or discharge from the high tension terminal at the outer end of the insulator to said inward crimp and said shell.

10. A spark plug comprising a metallic shell,

4 assume an insulator having an inner portion di awash in comprising a layer of electrical insulating matethe shell and an outer portion projecting outrial bonded to said means and to the outer end wardly therefrom, means including an inward of said shell and capable of withstanding high crimp on the cut: end 01 the shell for securing temperature and also being chemically inert in and hermetically sealing the insulator to the shell, its environment. a high tension terminal projecting beyond the 14. A spark plug comprising a metallic shell, outer end 01' the insulator. and a cap oi! elastic an insulator having an inner portion disposed electrical insulating material surrounding and in in the shell, and an outer portion projecting outstretched engagement with the outer portion oi! wardly therefrom, cooperating structure on the the insulator immediately above said inward shell and on the portion oi the insulator disposed crimp and coniorming to the contour of and covtherein and including metallic means at the outer ering said crimp and overlying the outer end of end of the shell ior securing and hermetically said shell, the outer portion of the insulator prosealing the insulator to the shell, a high tension jecting beyond said cap and coacting therewith terminal projecting beyond the outer end of the to provide a high and eflective resistance to elec- 5 insulator, and a cap of electrical insulating matetrical flash-over or discharge from the high tenrial surrounding the part 01 the peripheral surlion terminal at the outer end of the insulator face of the outer projecting portion of the insutoauid metallic means and said shell. lator adjacent said means and covering said 11. A spark plugcomprising a metallic shell, means and the outer end of the shell, said cap an insulator having an inner portion disposed in comprising a coating of electrical insulating the shell and an outer portion projecting out" material. wurdly therefrom, means including an inward 15. A spark plug comprising a metallic shell, crimp on the outer end of the shell for smturlng an insulator having an inner portion disposed in and hermetically Se ling the insulator to the the shell, and an outer portion projecting out shell, as high tension terminal p ojecting yond warclly therefrom, cooperating structure on the the outer end of the insulator, and a cap of elasshell and on the portion oi the insulator disposed tic electrical insulating ate l S o d and therein and including metallic means at the outin stretched ng fi t with and Cemented to or end of the shell for securing and hermetically the outer p tl nillifi, the insulator immediately sealing the insulator to the shell, a high tension above sa d n d and ing to the ,30 terminal projecting beyond the outer end of the contour of and covering d crimp a s r sc insulator, and a cap of electrical insulating matethe outer end 01 said h l. t m D rial surrounding the part oi the peripheral surthe mi p l ll nd saliiiti lllilifl oil tho outer projecting portion of the insuwlcfl therewith to P e high and iator adjacent said means and covering said tive resistance to electrical fiashwvel means and the outer end of the shell, said cap cha from the high tension llfil'mllllfill 131 i. an insulating coating of synthetic outer end of the insulator to said metallic moms and said shell. iii, A spark plug comprising a metallic shell, 12. A spark p g Comprising a m :Lui. iniszuiator having an inner portion disposed an insulator ha an inner portion the shell, and an outer portion projecting outthe shell and an outer portion P y therefrom, cooperating structure on the flfd Y therefrom, mea fi li' 1 r h and on the portion of the insulator disposed 011ml) 0!! the Outer end 01 the 511ml fill scour-ins therein and including metallic means at the outand hermetically sealing the insulator to the shell, end f the Shell f ecuring and hermetjcany a high tension terminal projecting beyo d sealing the insulator to the shell, a high tension outer end of the insul or. a d it -i iinal projecting beyond the outer end of the electrical insu mflierial Surmlmllim ilutor, and a cap of electrical insulating matestretched engagement with ml? M surrounding the part of the peripheral sur-- the insulator lmmedialleli Elbow lace of the outer projecting portion of the incl'lml and Conforming to the contour": of) sulator adjacent said means and covering said 911118 B crimp and overlying the Outer 1 "means and the outer end of the shell, said cap said shell. th 0 1 Portion 01 will illlllllbll i n cruu gririuirig a coating of insulating cement. lecti z beyond said cap and 1030mm g w 17, A, spark plug comprising a metallic shell, to prov 111311 and efiecmve t or ttfll having an inner portion disposed in trlcal fl discharge fmml high! the hell, and an outer portion projecting outaion terminal at the outer end of the insulator th f m cooperating Structure on the to said metallic means and said stroll. t e ltlttlr shell and on the portion 0! the insulator disposed P031011 01 the insulator havmg H llltlwnwnim *1 in and including metallic means at the outm! Shoulder immediately above; m d of the shell for securing and hermetically I 8 with the top 0! the 1mm scaling the insulator to the shell, a high tension Positively retain it in Position terminal projecting beyond the outer end of the 13. A spar 1 8 comprising U in ator, and a cap of electrical insulating maan insulator having an inner D urrounding the part of the peripheral surthe she l, and an outer portion the outer projecting portion of the inwardly t f D N? vjaccnt said means and covering said shell and on the po tio of e 11 U1 and the outer end of the shell, said cap therein and including metallic means my coating of insulating enamel of high end 01! the shell for securing arur'i l m ugngtant, sealing the insulator to the shell, A spark plug comprising a metallic shell, terminal projecting beyond th ulotcr having an inner portion disposed in insulator, and a cap of electrical i, and an outer portion projecting outte -15,] urrounding the part of the 11, therefrom, cooperating structure on the face of the outer projecting ortion of till i and on the portion of the insulator disposed lator adjacent said means and covering soil! therein d including metallic means at the outmean; and the outer end of tho shell, ilitlijt, cup 315 cud of the shell for securing and hermetically sealing the insulator to the shell, a high tension terminal projecting beyond the outer end oi the insulator, and a cap oi electrical insulating material surrounding the part oi the peripheral suriace oi the outer projecting portion oi the insulator adjacent said means and covering said means and the outer end oi the shell, said cap comprising an insulating coating oi paint oi high dielectric constant.

19. A spark plug comprising a metallic shell, an insulator having an inner portion disposed in the shell, and an outer portion projecting outwardly thereirom, cooperating structure on the shell and on the portion oi the insulator disposed therein and including metallic means at the outer end of the shell ior securing and hermetically sealing the insulator to the shell, a high tension terminal projecting beyond the outer end oi the insulator, and a cap oi electrical insulating material surrounding the part of the peripheral suriace oi the outer projecting portion oi the insulator adjacent said means and covering said means and the outer end oi the shell, said cap comprising a plastic insulating coating oi high dielectric constant.

20. A spark plug comprising a metallic shell, an insulator having an inner portion disposed in the shell and an outer portion projecting outwardly thereirom, cooperating structure on the shell and on the portion oi the insulator disposed therein and including metallic means at the outer end oi the shell ior securing andhermetically sealing the insulator to the shell, said shell having a hexagon formation at its outer end just inwardly of said metallic means, ,a high tension terminal projecting beyond the outer end oi the insulator, and a cap of electrical insulating ma.-

terial covering and coniormlng to the'contour oi said metallic means and in tight surface-tosuriace engagement with the part oi the peripheral surface oi the outer projecting portion oi the insulatoradjacent saidmeans, the cap lying, entirely within the confines oisaid hexagon' iormation, the outer portion oi the insulator projecting beyond the cap, the cap coacting with ,the portion oi the insulator extending between v the cap and the high tension terminal to provide a high and eiiective resistance to electrical flashover or discharge from the high tension terminal to said means. a

21. A spark plug comprising a metallic shell,

an insulator having an innenportion disposed in the shell and an outer portion projecting outwardly thereirom, cooperating structure on the shell and on the portion oi the insulator disposed therein ior securing and hermetically sealing the insulator to the shell, a high tension terminal projecting beyond the outer end oi the insulator, and a cap oi electrical insulating material covering and coniorming to the contour oi the portion oi'saidcooperating structure located at the outer 25 end oi the shell and in tight suriace-to-suriaoe engagement with the part oi the peripheral suriace oi the outer projecting portion oi the insulator adjacent said portion oi said cooperating structure, the outer portion oi the insulator projecting beyond said cap, the cap coacting with the portion oi, the insulator extending between the cap and the high tension terminal to provide a high and eiiective resistance to electrical flash over or discharge irom the high tension terminal to the outer end oi the shell.

cums a, some. 

